Multistream packet transfer systems are known as digital display interfaces suitable for linking video sources to video display devices. With such a multistream packet transfer system, for example, one or more packet streams can be transferred simultaneously through a “virtual pipe” established within a physical link (for example, refer to Japanese Laid-Open Patent Publication No. 2009-9106). Optical network units (ONUs) and optical line terminators (OLTs) having traffic control functions are known in relation to systems carrying out data communication. For example, an ONU and an OLT monitor data accumulation for each priority class queue and transmit pause frames with priority class queue numbers to a network in the user's home and to a higher level network in order to request pausing/restarting of traffic transfer in priority class units. The ONU and the OLT receive, from the user's home or the higher level network, pause frames with priority class queue numbers, set the numbers in the priority class queue scheduler, and pause/restart traffic transfer in priority class units (for example, refer to Japanese Laid-Open Patent Publication No. 2007-194732).
In mobile communication systems, data of multiple streams is collectively transmitted between stations, such as a radio network controller (RNC) and a base station, for example. The data of multiple streams is collectively transmitted in data units, such as packets, for example. In such a case, if data is resent in a stream transmitting a larger amount of data or a stream with disrupted data transmission due to failure, etc., the data resending process is performed with priority. Thus, there is a problem in that even when data with high priority exists in another stream, this data with high priority is not transmitted until the resending process is completed.